U.S. Pat. No. 7,363,898 discloses a valve timing control device configured to start an engine, with a driving side rotational member and a driven side rotational member being interlocked. According to U.S. Pat. No. 7,363,898, the valve timing control device includes a locking member and an engaging recess portion provided between/across the driving side rotational member and the driven side rotational member. And, when the engine is stopped, a spring member brings the locking member and the engaging recess portion into engagement with each other in response to discharge of operational oil of the valve timing control device.
For enabling this engagement between the locking member and the engaging recess portion, it is required that the driving side rotational member and the driven side rotational member be in alignment with each other at a predetermined position. For this reason, in the case of the valve timing control device disclosed in U.S. Pat. No. 7,363,898, there is provided a phase displacement restricting mechanism for restricting relative rotation between the locking member and the engaging recess portion within a predetermined angular range, thereby to restrict the relative positions between the locking member and the engagement recess portion within a predetermined range.
This phase displacement restricting mechanism includes an projecting/retracting member (“insertion member”) provided in the driven side rotational member and a recess portion provided in the driving side rotational member and capable of retaining the projecting/retracting member. The projecting/retracting member is projected or retracted by operational oil fed into an advanced angle chamber of the valve timing control device, at the time of startup of the engine. In other words, the projecting/retracting member functions to maintain the driving side rotational member and the driven side rotational member under the interlocked state until the operational oil pressure of the valve timing control device builds up at the time of start of the engine. Once the engine has started, the operational oil releases the projecting/retracting member and the locking state by the locking member. With this, the driving side rotational member and the driven side rotational member become rotatable relative to each other and the relative phase between these two rotational members is appropriately controlled through control using the operational oil.
Incidentally, desirably, the retracting movement of the projecting/retracting member should occur under the state of the operational oil being fed to both the advanced angle chamber and the retarded angle chamber at the time of the engine startup. For, if the projecting/retracting member is retracted to release the interlocked state when the operational oil is not fed to both the advanced angle chamber and the retarded angle chamber, the relative phase between the two rotational members cannot be retained, thus leading to deterioration in the engine startup performance. For this reason, the valve timing control device is provided with a valving element operable by operational oil fed thereto. The projecting/retracting member becomes movable after this valving element is activated.
However, at the time of stopping the engine, failure, if occurs, in the collaboration between the projecting/retracting member and the valving element could result in impossibility of fixing the driving side rotational member and the driven side rotational member under the interlocked state. For example, at the time of start of engine, by the operational oil fed to the retarded angle chamber, first, the valving element is changed in position to its start position, whereby communication is established between the advanced angle chamber and the projecting/retracting member, so that the oil from the advanced angle chamber causes the projecting/retracting member to be changed in position to the engagement releasing position. When the engine is stopped, these series of collaborative operations are carried out in reverse order. That is, in response to stopping of the engine, the operational oil is drained from the advanced angle chamber and the retarded angle chamber, so that the oil pressure drops. In response to this, first, the projecting/retracting member is moved to the retaining position and then the valving element is moved to its initial position.
However, due to an unexpected cause, the movement of the valving element may precede the movement of the projecting/retracting member. In this case, the communication between the driving side rotational member and the driven side rotational member will be blocked by the valving element, so that the projecting/retracting member becomes unable to protrude, thus failing to fix the driving side rotational member and the driven side rotational member to the interlocking phase. As a result, the next startup of the engine will become difficult.
Thus, a need exists for a valve timing control device having a phase displacement restricting mechanism which is not susceptible to the drawback mentioned above.